Projector systems with reduced flicker

ABSTRACT

An image display system is disclosed comprising an output unit and a means for displaying a plurality of color frames on the output unit. Each color frame is subpixelated and displayed over time. One of the color planes is a color plane of a low luminance color, and the low luminance color plane is displayed with greater frequency over time than other displayed color frames.

[0001] In commonly owned United States patent applications: (1) Ser. No.09/916,232 (“the '232 application”), entitled “ARRANGEMENT OF COLORPIXELS FOR FULL COLOR IMAGING DEVICES WITH SIMPLIFIED ADDRESSING,” filedJul. 25, 2001; (2) Ser. No. 10/278,353 (“the '353 application”),entitled “IMPROVEMENTS TO COLOR FLAT PANEL DISPLAY SUB-PIXELARRANGEMENTS AND LAYOUTS FOR SUB-PIXEL RENDERING WITH INCREASEDMODULATION TRANSFER FUNCTION RESPONSE,” filed Oct. 22, 2002; (3) Ser.No. 10/278,352 (“the '352 application”) entitled “IMPROVEMENTS TO COLORFLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS FOR SUB-PIXELRENDERING WITH SPLIT BLUE SUBPIXELS,” filed Oct. 22, 2002; (4) Ser. No.10/243,094 (“the '094 application), entitled “IMPROVED FOUR COLORARRANGEMENTS AND EMITTERS FOR SUBPIXEL RENDERING,” filed Sep. 13, 2002;(5) Ser. No. 10/278,328 (“the '328 application”), entitled “IMPROVEMENTSTO COLOR FLAT PANEL DISPLAY SUB-PIXEL ARRANGEMENTS AND LAYOUTS WITHREDUCED BLUE LUMINANCE WELL VISIBILITY,” filed Oct. 22, 2002; (6) Ser.No. 10/278,393 (“the '393 application”), entitled “COLOR DISPLAY HAVINGHORIZONTAL SUB-PIXEL ARRANGEMENTS AND LAYOUTS,” filed Oct. 22, 2002,novel subpixel arrangements are therein disclosed for improving thecost/performance curves for image display devices and hereinincorporated by reference.

[0002] These improvements are particularly pronounced when coupled withsubpixel rendering (SPR) systems and methods further disclosed in thoseapplications and in commonly owned United States patent applications:(1) Ser. No. 10/051,612 (“the '612 application”), entitled “CONVERSIONOF RGB PIXEL FORMAT DATA TO PENTILE MATRIX SUB-PIXEL DATA FORMAT,” filedJan. 16, 2002; (2) Ser. No. 10/150,355 (“the '355 application”),entitled “METHODS AND SYSTEMS FOR SUB-PIXEL RENDERING WITH GAMMAADJUSTMENT,” filed May 17, 2002; (3) Ser. No. 10/215,843 (“the '843application”), entitled “METHODS AND SYSTEMS FOR SUB-PIXEL RENDERINGWITH ADAPTIVE FILTERING,” filed May 17, 2002; (4) Ser. No. ______ (“the'______ application) entitled “IMAGE DATA SET WITH EMBEDDED PRE-SUBPIXELRENDERED IMAGE”, filed Apr. 7, 2003.

[0003] Additionally, the present application is also related to commonlyowned: (1) Ser. No. 10/047,995 (“the '995 application”) entitled “COLORDISPLAY PIXEL ARRANGEMENTS AND ADDRESSING MEANS” filed Jan. 14, 2002;(2) Ser. No. ______ (“______ application”) entitled “SUBPIXEL RENDERINGFOR CATHODE RAY TUBE DEVICES” filed May 20, 2003; (3) Ser. No. ______(“______ application”) entitled “IMPROVED PROJECTOR SYSTEMS” filed May20, 2003; and (4) Ser. No. ______ (“______ application”) entitled“IMPROVED IMAGE CAPTURE DEVICE AND CAMERA” filed May 20, 2003.

BACKGROUND

[0004] The above-referenced and commonly owned applications are herebyincorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The accompanying drawings, which are incorporated in, andconstitute a part of the specification, illustrate exemplaryimplementations and embodiments of the invention, and, with the detaileddescription, serve to explain principles of the invention.

[0006]FIG. 1 illustrates a side view of a prior art projector projectingimages, in a frontal view, to a central point on an imaging screen.

[0007]FIG. 2 illustrates a side view of a projector, projecting images,in a frontal view, to a central point on an imaging screen in which thethree colors are offset from each other.

[0008]FIG. 3A illustrates a side view of a prior art CRT projectingimages to a central point on an imaging screen.

[0009]FIG. 3B illustrates a portion of the phosphor screen of the priorart CRT illustrated in FIG. 3A, focusing Gaussian spots to a singlepoint on an imaging screen.

[0010]FIG. 4A illustrates a side view of a CRT projecting images to animaging screen in which the three colors are offset from each other.

[0011]FIG. 4B illustrates a portion of the CRT illustrated in FIG. 4Afocusing Gaussian spot to a phosphor screen in which the three colorspots are offset in the horizontal direction.

[0012]FIG. 4C illustrates a portion of the CRT illustrated in FIG. 4Afocusing Gaussian spot to a phosphor screen in which the green colorspots are offset in the diagonal direction.

[0013]FIG. 5 illustrates a prior art arrangement of pixels forelectronic information display projectors.

[0014]FIGS. 6, 7, and 8 illustrates an arrangement of pixels for each ofthe colors green, red, and blue, respectively.

[0015]FIG. 9 illustrates the arrangements of FIGS. 6, 7, and 8 overlaidon one another to show how a full color image is constructed.

[0016]FIG. 10 illustrates the overlaid image of FIG. 9 with one fullcolor logical pixel turned on.

[0017]FIGS. 11 and 12 illustrates the green and red image planes,respectively, with a single column of logical pixels turned on.

[0018]FIG. 13 illustrates the red and green image planes of FIGS. 11 and12 overlaid;

[0019]FIGS. 14A-14B and 15A-15B illustrate the green and red imageplanes, respectively, with two columns of logical pixels turned on.

[0020]FIGS. 16A and 16B illustrate the green and red image planes ofFIGS. 14A-14B and 15A-15B overlaid, respectively.

[0021]FIG. 17 illustrates two images of the pixel arrangement of FIG. 6overlaid, offset by one-half pixel, to demonstrate how a single imagingplane can build up a higher resolution image using field sequentialcolor, or to demonstrate how two imaging planes of a multi-panel may beoffset to build up a higher resolution image.

[0022]FIG. 18 illustrates splitting of an image path into two differentpaths for different colors through an inclined plate made of achromodispersive material.

[0023]FIG. 19 illustrates a prior art arrangement of pixels.

[0024]FIG. 20 illustrates an overlay of the arrangement of prior artFIG. 19 in which the two colors are offset by one-half pixel in thediagonal direction.

[0025]FIG. 21 illustrates the overlaid arrangement of FIG. 20 with twocolor logical pixels at different addressable points.

[0026]FIG. 22 illustrates the overlaid arrangement of FIG. 20 with analternative color logical pixel and a column line of logical pixels.

[0027]FIG. 23 illustrates an overlay of FIG. 8 for three colors in whichthe colors are offset by one-third pixel each, with one full colorlogical pixel turned on.

[0028]FIG. 24A is a chart showing the chromaticity coordinates of theemitters of a prior art three color display.

[0029]FIG. 24B is a chart showing the chromaticity coordinates of theemitters of an improved three color display, compared to thechromaticity coordinates of FIG. 24A.

[0030]FIG. 25 is a chart showing the chromaticity coordinates of theemitters of a novel four color display.

[0031]FIG. 26 is a chart showing the chromaticity coordinates of theemitters of a novel five color display.

[0032]FIG. 27 illustrates the reconstruction points of the prior artdisplay of FIG. 19 overlaid on the appearance of the display.

[0033]FIG. 28 illustrates the reconstruction points of the novel displayshown in FIG. 20.

[0034]FIG. 29 illustrates the arrangement of emitters and reconstructionpoints of a novel twinned projector arrangement with coincident colorplanes.

[0035]FIG. 30 illustrates the arrangement of emitters and reconstructionpoints of another novel twinned projector arrangement with displacedcolor planes.

[0036]FIGS. 31A and 31B illustrate a prior art arrangement of amulti-sensor chip camera in which all of the color plane sample areasare coincident, sampling an image and the resulting data setrespectively.

[0037]FIGS. 32A and 32B illustrate a novel arrangement of a multi-sensorchip camera in which two of the color plane sample areas are displaced,sampling an image and the resulting data set respectively.

[0038]FIGS. 33A and 33B illustrate a novel arrangement of a multi-sensorchip camera in which three of the color plane sample areas aredisplaced, sampling an image and the resulting data set respectively.

[0039]FIG. 33C is the illustrates displaying the processed image of FIG.33B onto a higher resolution, conventional prior art display.

[0040]FIGS. 34A and 34B illustrate a novel arrangement of color filterarray for a two chip color camera, one with a red/green checkerboard,the other a lower resolution sensor for imaging blue image component,respectively.

[0041]FIG. 35A illustrates a novel display arrangement of the colorplanes on a display.

[0042]FIGS. 35B, 35C, and 35D illustrate the color planes overlaid oneach other to create a full color image as shown in FIG. 35A.

[0043]FIGS. 36A and 36B illustrate how this moiré distortion iseliminated by the arrangement of FIG. 35A.

[0044]FIG. 37 illustrates a prior art color wheel filter of threecolors.

[0045]FIGS. 38A, 38B, 38C, and 38D illustrate novel color wheel filtersof three colors.

[0046]FIGS. 39A and 39B illustrates novel color wheel filters of threecolors and black.

[0047]FIG. 40 illustrates a novel color wheel filter of four colors, oneof which is white.

[0048]FIGS. 41, 42A, 42B, 42C, and 42D illustrate a spatial lightmodulator and a method of reducing data bandwidth, image size, whilemaintaining image quality using spatio-temporally displaced filteringand reconstruction.

DETAILED DESCRIPTION

[0049] Reference will now be made in detail to exemplary implementationsand embodiments of the invention, examples of which are illustrated inthe accompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.Furthermore, the following description is illustrative only and not inany way intended to be limiting.

[0050] Prior art projectors typically overlaps the three-color images(e.g. RGB) exactly coincidentally, with the same spatial resolution. Astaught in the '995 application, the color imaging planes are overlaidupon each other with an offset of about one-half pixel. By offsettingthe color imaging planes, an electronic image capture, processing, anddisplay having higher resolution images is created by increasing theresolution of the system.

Cathode Ray Tube Displays, Projector Displays, and Subtractive FlatPanel Displays

[0051]FIG. 1 is schematic of a prior art projector 100 having a lightbeam 102 that projects red (R), blue (B), and green (G) images 106 on toan imaging (or projection) screen 104. Prior art practices converge thered, the blue, and the green images to a point 110 on the projectionscreen 104. In contrast, FIG. 2 illustrates schematic of a projector 200having a light beam 202 that projects through an optical element (orlens) 204 red 206, blue 208, and green images 210 on to an imaging (orprojection) screen 212. As illustrated in this example, such a projectorwill separate and differentially shift the red, green, and blue images.Thus, the image is again formed, but the image is shifted optically toseparate the red, blue, and green color planes by about one-half pixel.

[0052] A similar procedure is used with a Cathode Ray Tube (CRT) videodisplay, as illustrated in prior art FIG. 3A. An electron gun 300projects an electron beam 302 inside the CRT 304 onto a phosphor surface306 with an array of color primary emitting phosphor dots. Prior artpractices converge the red, the blue, and the green image pixel to acircular Gaussian spot 308 on the phosphor surface 306. The CRT 304 candirect the electron beam 302 towards the phosphor surface 306electrostatically or magnetically. FIG. 3B illustrates a portion of thephosphor screen 306 in which the CRT focuses Gaussian spot 308 to asingle point on the phosphor screen 306.

[0053] In contrast, FIG. 4A shows a diagrammatic illustration of a CRTvideo display having electron guns 400 that project electron beams 402inside the CRT 404 onto a phosphor surface 406. As illustrated in thisexample, CRT 404 will separate and differentially shift the red 416,green 420, and blue 418 images 408. This can be accomplished bymisconverging the electron beams with steering electronics, such as yokecoils, electrostatic deflection plates, or by appropriately displacingthe electron guns. Thus, the image is again formed, but the image isshifted to separate the red 416, blue 418, and green 420 color planes byabout one-third pixel or by shifting just the green 420 color plane byone-half pixel. FIG. 4B illustrates the portion of the phosphor screenin which the CRT focuses so that pixel color spot 408 consists of red416, green 420, and blue 418 spots that are offset by one-third pixel inthe horizontal direction. This modification allows CRTs so adjusted touse the very same subpixel rendering techniques utilized in the art onconventional RGB stripe architecture liquid crystal display (LCD)panels. FIG. 4C illustrates a portion of the phosphor screen 406 inwhich the CRT focuses the Gaussian spots so that the green 420 colorspot is offset by one-half pixel in the diagonal direction from theconverged red 416 and blue 418 spots.

[0054] Subpixel rendering can also be supported on conventional CRTswithout major modification to the CRT. Instead, the timing of the datagoing to the CRT is modified. This could be accomplished by amodification of the video graphics card on a computer.

[0055] In one embodiment, one dimensional subpixel rendering could besupported. For example, the red data would lead, the green delayed byone third (⅓) of a pixel clock, the blue delayed by two thirds (⅔) of apixel clock. This can be accomplished by using a “subpixel clock” (shownschematically as element 422 in FIG. 4A) at three times the usual pixelclock for the data D/A converters. The result will be that a single“pixel” will paint displaced red 416, green 420, and blue 418 spots asshown in FIG. 4B. This modification could be made to the video graphicscard and would make a CRT look like an RGB stripe LCD and compatiblecommercial subpixel rendered text such as that disclosed in Hill, etal., U.S. Pat. No. 6,188,385. It might be advantageous to use a systemto turn on and off the new mode, either globally or locally by detectingthe presence of the subpixel rendered text using a suitable method, asdisclosed in the '______ application noted above.

[0056] It is also possible to simulate a two dimensionally subpixelatedflat panel display. For example, the timing of the color data could beswitched every row. The odds rows will have the red data lead with thegreen data delayed by one half (½) of a pixel clock. On the even rows,the green data will lead while the red data is delayed by one half (½)pixel clock. The blue data is always delayed by one third (⅓) of a pixelclock. The pixel clock is half the frequency of a “normal” pixel clock.

[0057] The above system will allow presubpixel rendered images to bedisplayed on the CRT with minimal processing. Further, the CRT cansupport higher resolution than ordinarily possible by doubling thenumber of rows, doubling the horizontal frequency, while using the samebandwidth amplifiers, cables, and memory.

[0058] Contrary to prior art projectors, subtractive flat panels, or tCRT displays which are not subpixelated, the projectors, subtractiveflat panel displays, or CRT displays discussed herein are subpixelatedand may thus take advantage of subpixel rendering techniques.

[0059] Multi-image plane color projectors often use a single white lightsource that is broken into narrower spectral regions and separate beampaths through the use of dichroic beam splitting filters. The separatedcolors illuminate separate spatial light modulators. The modulated lightis bought back together and focused onto an imaging screen to be viewedas a full color image.

[0060]FIG. 5 illustrates a prior art arrangement 510 of square pixels512, and in this example, forming an array of 12×8 pixels. For prior artprojection or subtraction displays, three planes of 12×8 pixels would beoverlaid to create a set of 12×8 logical pixels. This is a total ofninety-six (96) pixels comprising two-hundred-eighty-eight (288) colorelements.

[0061]FIGS. 6, 7, and 8 are illustrate an arrangement of pixel imagesfor each color of green, red, and blue, respectively, for projectors.The same FIGS. 6, 7, and 8 are also illustrations of an arrangement ofsubpixels for each color of magenta, cyan, and yellow, respectively, forsubtractive color flat panel displays. Magenta is equivalent tosubtracting green from white. Cyan is equivalent to subtracting red fromwhite. While yellow is equivalent to subtracting blue from white. Forexample, a multispectral light source is illuminated, illuminatingpanels of magenta, cyan, and yellow that are offset from one another inx and y by substantially less than 100%. In the following discussionsregarding the theory of operation of the arrangement of subpixelelements, the additive color projector is used as an example. However,for subtractive flat panel display, the same theory of operation appliesif one applies additive to subtractive color transforms well known inthe art.

[0062]FIG. 9 illustrates the resulting multipixel image 20 of overlayingthe images 14, 16, and 18 of FIGS. 6, 7, and 8, respectively, for athree-color plane projector or subtractive flat panel display. Theresulting multipixel image 20 of FIG. 9 has the same number of logicalpixels 24 as illustrated in FIG. 10 and the same addressability and MTFas the image formed by the arrangement of prior art FIG. 5. However, thesame image quality is achieved with only one-hundred-twenty-three (123)color elements, less than half of the number required by the prior artarrangement illustrated in FIG. 5. As the costs increase with the numberof elements, the reduction in the number of elements offers the sameimage quality at a significantly lower cost, significantly higher imagequality at the same cost, or a higher image quality at lower cost, whencompared to the prior art arrangement illustrated in FIG. 5.

[0063] In each of the imaging devices discussed above, the beams (orpanels) are convergent by substantially less than about 100%, with lessthan about 75% preferred, and with about 50% more preferred.

[0064] One advantage of the three-color plane array disclosed here isimproved resolution of color displays. This occurs since only the redand green pixels (or emitters) contribute significantly to theperception of high resolution in the luminance channel. Offsetting thepixels allows higher perceived resolution in the luminance channel. Theblue pixel can be reduced without affecting the perceived resolution.Thus, reducing the number of blue pixels reduces costs by more closelymatching human vision.

[0065] The multipixel image 22 of FIG. 10 illustrates a logical pixel 24showing a central pixel 26 of either the red or the green color plane(in this case it is green) that is set at 50% of the input valueassociated with that logical pixel 24. Surrounding and overlapping thiscentral pixel 26 are four pixels 28 of the opposite color of thered/green opposition channel (in this case it is red) that is set at12.5% of the input value associated with that logical pixel 24.Partially overlapping and offset is a blue pixel 30, which is set atabout 25% of the input value associated with that logical pixel 24.

[0066] The logical pixel 24 of FIG. 10 illustrates that the central areadefined by the central pixel 26 is the brightest area, at 31.25%, whilethe surrounding area, defined by the surrounding pixels 28 of the“opposite” color (not overlapping with the central pixel 24) remains at6.25% brightness. This approximates a Gaussian spot, similar to thoseformed by the electron gun spot of a CRT.

[0067] Images 52 and 68 are built up by overlapping logical pixels asshown in FIGS. 13 and 16, respectively. For ease of illustration, theblue plane in each figure has not been shown for clarity. Thearrangement of the pixels of each color plane 14, 16, and 18 illustratedin FIGS. 6, 7, and 8, respectively, are essentially identical to some ofthe effective sample area arrangements found in many of theabove-referenced applications that are incorporated by reference.Further, the arrangement of this present embodiment use the samereconstruction points of the pixel arrangements disclosed in theabove-referenced applications.

[0068] For projected image or subtractive color flat panel displays, thepresent application discloses using the same pixel rendering techniquesand human vision optimized image reconstruction layout. However, asmoother image construction is created in the present application due tothe overlapping nature of the pixels. For an example of a multipixelimage 52 having the smoother image construction, FIG. 13 illustrates avertical line 54 comprising the green component image 40 and the redcomponent image 50 of FIGS. 11 and 12, respectively. As illustrated inthe multipixel image 40 in FIG. 11, a vertical line 41 comprises centralgreen pixels 42 and outer green pixels 44. As illustrated in themultipixel image 50 in FIG. 12, a vertical line 51 comprises central redpixels 46 and outer red pixels 48. For clarity, the blue color plane isnot shown in FIG. 13. This example assumes that the vertical line 54displayed at about 100% of the input value and is surrounded on bothsides by a field at 0% of the input value.

[0069]FIG. 13 illustrates that the central red pixels 46 of the verticalline are offset from the central green pixels 42 when superimposed ontoeach other. These central pixels 42 and 46 are each set at 75%. Theouter pixels 44 and 48 are each set at 12.5%. The areas of overlap ofthe central pixels 42 and 46 form a central series of smaller diamonds56 that are at 75% brightness. The overlap of pixels 44 and pixels 46,and the overlap of pixels 48 and pixels 42, respectfully, form twoseries, just outside of the said central series, of smaller diamonds 58that are at 43.75% brightness. The overlap of the outer pixels 44 and 48form two series of smaller diamonds 60 that are at 12.5% brightness.While the areas of the outer pixels 44 and 48 that do not overlap forman outermost series of smaller diamonds 62 that are at 6.25% brightness.This series of brightness levels, 6.25%, 12.5%, 43.75%, 75%, 43.75%,12.5%, and 6.25% exhibits a Gaussian distribution. Further, if one wereto imagine an infinitely narrow vertical line segment, at least severalpixels long, moving across the displayed vertical line 54, integratingthe brightness, the resulting function would be a series of smoothsegments joining the brightness levels, from zero to 75% to zero. Thus,the resulting cross-sectional brightness function, integrated overseveral pixels tall, along the displayed line, closely approximates asmooth Gaussian curve. This displayed vertical line can be moved over byabout one-half pixel, such that the addressability would be aboutone-half pixel.

[0070] In moving the vertical line, the amount of improvement isproportional to the amount that the red and green planes are out ofphase. Having the image planes out of phase at a value of substantiallyless than about 100% is preferred, with less than about 75% morepreferred, and with the images being exactly out of phase by aboutone-half pixel, or about 50%, is ideal.

[0071]FIGS. 16A and 16B illustrate two multipixel images 68 and 68 b oftwo vertical lines 69 and 69 b, respectively, displayed to demonstratethat the MTF is about one-half of the addressability, which is thetheoretical limit for subpixelated displays. FIG. 16A illustrates thetwo vertical lines 69 comprising the green component image 64 and thered component image 66 of FIGS. 14A and 15A, respectively. Asillustrated in the multipixel image 64 in FIG. 14A, the central greenpixels 70 and outer green pixels 72 comprise two vertical lines 65. Asillustrated in the multipixel image 66 in FIG. 15A, the central redpixels 76 and outer red pixels 78 comprise two vertical lines 67. Forclarity, the blue color plane is not shown in FIG. 16A. This exampleassumes that the vertical line 69 is displayed at about 100% of theinput value and is surrounded on both sides by a field at 0% of theinput value.

[0072] The central red pixels 76 of the two vertical lines 69 are offsetfrom the central green pixels 70 when superimposed as in FIG. 16A. Thesecentral line pixels 70 and 76 are each set at 75%. The outer pixels 72and 78 are each set at 12.5%. The pixels 74 and 80 between the twocentral lines of pixels 76 and 70 are set at 25%.

[0073] The outer edges, those not adjoining the other line, have thesame sequence of brightness levels as described for the case of FIG. 13.That is, the areas of the outer pixels 72 and 78 that do not overlapform an outermost series of smaller diamonds 88 at 6.25% brightness. Theoverlap of the outer pixels 72 and 78 form two series of smallerdiamonds 84 that are at 12.5% brightness. The overlap of pixels 72 andpixels 76, and the overlap of pixels 78 and pixels 70, respectfully,form two series, just outside of the central line series 86, of smallerdiamonds 82 that are at 43.75% brightness. The areas of overlap of thecentral line pixels 70 and 76 form a central series of smaller diamonds92 that are at 75% brightness.

[0074] The space between the two central vertical lines 69 has threeseries of smaller diamonds 90 and 94. The overlap of red central linepixels 76 and green interstitial pixels 74, and the overlap of greencentral line pixels 70 and red interstitial pixels 80, respectively,form a series of smaller diamonds 90 at 50% brightness. The overlap ofinterstitial pixels 74 and 80 form a series of smaller diamonds 94 at25% brightness. Theoretically, this represents samples of a sine wave atthe Nyquist limit, exactly in phase with the samples. However, whenintegrating over an imaginary vertical line segment as it moves acrossfrom peak to trough to peak, the function is that of a triangle wave.Yet, with the MTF of the projection lens limiting the bandpass of theprojected image, the function is that of a smooth sine wave. The displayeffectively removes all Fourier wave components above the reconstructionpoint Nyquist limit. Here, the modulation depth is 50%. As long as thisis within the human viewer's Contrast Sensitivity Function (CSF) for agiven display's contrast and resolution, this modulation depth isvisible.

[0075]FIG. 16B illustrates the two vertical lines 69 b comprising thegreen component image 64 b and the red component image 66 b of FIGS. 14Band 15B, respectively. These images are designed to be ‘sharper’ thanthose of FIGS. 16A, 14A, and 15A. As illustrated in the multipixel image64 b in FIG. 14B, the green pixels 70 b comprise two vertical lines 65b. As illustrated in the multipixel image 66 b in FIG. 15B, the redpixels 76 b comprise two vertical lines 67 b. For clarity, the bluecolor plane is not shown in FIG. 16B. This example assumes that thevertical lines 69 b are displayed at about 100% of the input value andis surrounded on both sides by a field at 0% of the input value. Here,the values of both the red pixels 76 b and the green pixels 70 b are setat 100% output value, while the pixels, 74 b and 80 b, between thedouble lines 67 b and 65 b are set at 0% output value. Likewise thepixels, 72 b and 78 b, outside the double lines 67 b and 65 b are set at0% output value. These values are generated by using sharpeningcoefficients in the filter matrix used in the subpixel renderingoperation.

[0076]FIG. 17 illustrates an overlay 96 of the image 14 of FIG. 6 offset50% with itself. This represents an alternative embodiment of a singlepanel projector, using field or frame sequential color that is wellknown in the art. In this embodiment, the array is again formed fromdiamonds, but the image 14 is shifted optically to separate the red andgreen color planes by about one-half pixel. This color shift may beaccomplished as shown in FIG. 18 by an inclined plane lens 98 of asuitable chromodispersive transparent material. Such an arrangement willseparate and differentially shift the red, green, and blue images due tothe different index of refraction for each wavelength. This lens elementmay be a separate flat plane lens, or may be an inclined curved elementthat is an integral part of the projection lens assembly. Suchmodifications to the lens assembly may be designed using techniques wellknown in the art.

[0077] These optical and mechanical means for shifting the color imageplanes can be used to improve display systems that use prior artarrangements 100 of pixels as illustrated in FIG. 19. The green image102 may be shifted from the red image 104 by about one-half pixel in thediagonal direction as illustrated in the arrangement 106 in FIG. 20.This allows subpixel rendering to be applied to the resulting system.FIG. 21 illustrates two logical pixels centered on a square grid thatlies on corner interstitial 108 and edge interstitial 110 points in thearrangement 106 of FIG. 20. FIG. 22 illustrates arrangement 106 with alogical pixel and a column line 112 of overlapping logical pixelscentered on pixel quadrants defined by the pixel overlaps.

[0078] In examining the example of a logical pixel 114, 116, and 118shown in FIG. 22, the output value of each pixel is determined by asimple displaced box filter in which four input pixels are averaged foreach output pixel. Each input pixel uniquely maps to one red outputpixel 114 and one green output pixel 118 that overlaps by one quadrant116. Thus, the addressability of the display has been increased fourfold, twice in each axis. With one input pixel at about 100% valuesurrounded by a field at 0% value, the red output pixel 114 and thegreen output pixel 118 are set at 25% output. The area of overlap 116 isat 25% brightness while the areas of the output pixels 114 and 118 notoverlapping are at 12.5% brightness. Thus, the peak brightness is in theoverlapping quadrant.

[0079] In examining the vertical line 112 displayed in FIG. 22, it isdisplaying a line at about 100% input value surrounded on both sides bya field at 0% input value. The overlapping logical pixels are additive.Thus, the red output pixels 120 and the green output pixels 124 are setat 50%. The area of overlap 122 is at 50% brightness while the areas ofthe output pixels 120 and 124 that are not overlapping are at 25%brightness. Thus, the area of peak brightness corresponds with locationof the displayed line 112.

[0080] In examining and evaluating the display system, it can be notedthat while the addressability of the display has been doubled in eachaxis, the MTF has been increased by a lesser degree. The highest spatialfrequency that may be displayed on the modified system is about one-halfoctave higher than the prior art system. Thus, the system may display2.25 times more information on four times as many addressable points.

[0081] In the above systems the blue information has been ignored forclarity. This is possible due to the poor blue resolving power of humanvision. However, in so far as the blue filter or other blue illuminationsystem is less than perfect and allows green light that will be sensedby the green sensing cones of human vision, the blue image will besensed by the green cones and add to the perception of brightness in theluminance channel. This may be used as an advantage by keeping the bluepixels in registration with the red pixels to add to the red brightnessand to offset the slight brightness advantage that green light has inthe luminance channel. Thus, the red output pixels may be, in fact, amagenta color to achieve this balance of brightness.

[0082] If a system were designed in which the “blue” image hassignificant leakage of green, and possibly yellow or even red, the“blue” image may be used to further increase the effective resolution ofa display. The “blue” color may be closer to a pale pastel blue, a cyan,a purple, or even a magenta color. An example of such a display 126 isillustrated in FIG. 23. FIG. 23 illustrates three images of the array ofpixels shown in FIG. 8 overlaid with a shift of one third of a pixeleach. A logical pixel 128 is illustrated on the resulting image 126 inFIG. 23. The red pixel 130, green pixel 132, and “blue” pixel 134overlap to form a smaller triangular area 136 that is at the center ofthe logical pixel. This overlap area is brightest, followed by the threeareas where there are only two pixels overlapping, while the areas withno overlap have the lowest brightness. The manner of calculating thevalues of the pixels follows in a similar manner as outlined above.

[0083] Another embodiment of the present invention is shown in FIG. 35Ain which the red 3504, blue 3502, and green 3506 color planes shown inFIGS. 35B, 35C, and 35D respectively are overlaid one another to formthe full color arrangement 3510. The color planes are overlaid eachother such that they are substantially “out of alignment” as shown inFIG. 35A.

[0084] This arrangement is characterized by having a green plane 3506that is higher resolution than both the red 3504 and blue 3502. In thispresent arrangement, the red 3504 and blue 3502 have the sameresolution, but this need not be the case. It is contemplated that allthree of the color planes might be different resolutions. For example,one might use the high resolution green color plane 3506 of FIG. 35D,with the red color plane 3504 of FIG. 35B, and the blue color plane 18of FIG. 8, overlaying thus such that they are all substantially “out ofalignment”. Alternatively, the red color plane may be the higher of thethree planes. However, in practice, given the luminances found in mostprojector systems, the green color plane will be found to be the bestchoice for the highest resolution.

[0085] More particularly, if the green luminance is approximately halfthe total luminance, as is commonly found in projectors, there may be anadvantage to the particular arrangement shown in FIG. 35A in which thegreen color plane 3506 is twice that of the red 3504 and blue 3502 colorplanes. This is not to say that the resolution ratio is determined bythe luminance ratio, rather it is the fact that one can achieve the sameresolution from the offset red 3504 and blue 3502 color planes as fromthe green color plane 3506 alone. These are then set to be substantiallyoffset from one another, the green 3506 from the virtual magenta(combined red 3504 and blue 3502). The advantage found in thisarrangement is that moiré distortion when reconstruction a highresolution image may be significantly reduced with a minimal number ofcolor reconstruction points.

[0086] Moiré distortion occurs when the desired signal is 90° out ofphase with the reconstruction points of the display. For example, if oneis attempting to display a single pixel wide line halfway between twopixels, the two pixels would be set to 50%. One could still see that thetotal signal strength and position is present, but the image is not assharp. If two single wide lines were to be displayed with only a singlepixel between them, but offset by half a pixel, then the two grey lineswould be smeared together, and it would no longer be distinguishablefrom a wide grey line. FIGS. 36A and 36B illustrate how this moirédistortion is eliminated by the arrangement of FIG. 35A. When narrowlines 3515 are in phase with the pixels of the green color plane 3506,the lines are out of phase by 90° for both the red 3504 and blue 3502color planes as shown in FIG. 36A. When the narrow lines 3515 b are outof phase with the pixels of the green color plane 3506, the lines are inphase with the red 3504 and blue 3502 color planes as shown in FIG. 36B.

Twinned Projectors

[0087] In the prior art, when brightness is required that is beyond thecapability of a single projector to supply, two projectors may be used.The images are conventionally converged 100%, as if the twinned unitswere in fact one unit. The combined image might be like that shown inFIG. 27, which shows the fully converged pixels 2705 and the associatedreconstruction points 2701. The image may have twice the brightness ofthat from a single projector, but has the same resolution.

[0088] One improvement of this system may be to displace the full colorpixel images from one of the projectors by one-half pixel in thediagonal direction as shown in FIG. 29. This gives similar, and in someaspects superior, performance improvements as that of the displacedcolor planes of FIGS. 20, 21, 22, and 28. FIG. 28 shows the displacedcolor arrangement of FIGS. 20, 21, and 22, and the associated colorplane reconstruction points 2801 and 2803. Comparing FIGS. 28 and 29illustrate the differences. FIG. 29 has full color reconstruction points2901 at each position where FIG. 28 has either a first color (e.g. red)2801 or second color (e.g. green) 2803 reconstruction point. Thus, formonochrome images, the twinned projector arrangement of FIG. 29 issimilar to the single projector arrangement of FIG. 28. However, forhighly saturated color images, the increased addressability of thetwinned projector arrangement of FIG. 29 allows a single color to havetwice as many reconstruction points.

[0089] A further improvement for twinned projectors is to displace thecolor planes of both projectors. One of the projectors has thearrangement shown in FIG. 28, while the other has the mirrorarrangement, resulting in the overlapped and fully displaced four imageplanes of FIG. 30. This arrangement has the same saturated color imagequality as that of FIG. 29, but has additional monochromeaddressability, resulting in significantly improved overall imagequality when suitably subpixel rendered.

[0090] Any system that traditionally uses converged, overlapped colorand/or white pixels can take advantage of the concepts taught herein.Examples given above included a color CRT display used for computermonitor, video, or television display may also be improved by shiftingthe color components and applying appropriate subpixel renderingalgorithms and filters. A simple and effective change for computermonitors is to shift the green electron spot as described above for FIG.4B and FIG. 22. This deliberate misconvergence will seemcounter-intuitive to those most knowledgeable in the CRT art, but theresulting improvement will be as described above. The displacement ofthe multi-color display imaging planes by a percentage of a pixelcreates a display of higher resolution images by increasing theaddressability of the system. Additionally, the MTF is increased tobetter match the design to human vision. A projector system using threeseparate panels can be optimized to better match the human vision systemwith respect to each of the primary colors. These results can beachieved in a single panel, field sequential color projector using aninclined plane chromodispersive lens element.

Film Scanners, Cameras, and Film Printers

[0091] The improvements and arrangements described herein may also helpimage capture and printer devices.

[0092] One embodiment may be an improved video or still camera. Someprior art cameras use multi-chip sensors, along with color filters ordichroic beam splitters. These may be considered to be the inverseoperations of the projectors described herein, and may benefit from thesame or similar arrangements of pixels. For example, FIG. 27 mayrepresent the arrangement of fully converged color planes of a prior artmulti-chip color camera. FIG. 28 may represent the offset color planearrangement of a multi-chip color camera. Such an arrangement may beformed by offsetting one or more of the sensor chips such the imageformed upon it is displaced by substantially one-half pixel. This wouldcreate a camera that directly and automatically captures and delivers asubpixel rendered data set. If the data set were delivered for displayto a projector with the same resolution and arrangement, then the imagedata set would need no further processing, and yet provide a superiorimage than a conventional, fully converged, camera, image data set, andprojector arrangement. Thus, the entire system, from image capture todisplay, is a matched, improved, system. Such a system performs asthough it was a higher resolution system with perceptually encoded“lossless” compression.

[0093]FIG. 31A shows a prior art arrangement of fully converged sensorelements sampling an exemplary image, in this case a “w” character,giving rise to the resulting image data set shown in FIG. 31B. It is tobe understood that any natural image will behave in like manner. Whenthe same exemplary image “w” is potentially sampled by a novel sensorarrangement (such as shown in FIG. 28), the resulting image data set isillustrated in FIG. 32B. FIGS. 31B and 32B may also be seen asrepresenting the resulting images of projecting, displaying theresulting data sets on matching projector systems, a prior art projectorin the case of FIG. 31B and the novel projector of one embodiment of thepresent invention in the case of FIG. 32B. Comparing the resulting imagequality, the novel system represented by FIG. 32B would be animprovement over that of the prior art. If the system analysis isextended to three offset image capture planes and projector planes, asshown in FIGS. 33A and 33B respectively, the image quality continues toincrease.

[0094] Similarly, the pixel arrangements of FIGS. 6, 7, and 8 may beused to capture images on a sampling plane that appears as that shown inFIG. 9. Again, when the resulting captured image data set is directlydisplayed on a matching projector or flat panel display, the imagequality will be superior to that of the prior art systems.

[0095] With multi-chip image sensors, each having independent electronicshutter control, creating the image data set to be displayed onmatching, or at least compatible, display means, another improvement ispossible—namely, reduced jutter. Jutter occurs when objects that moveacross a scene are displayed in a series of still frames at a moderatelylow rate, such as the twenty-four (24) frames per second for film, ortwenty-five (25) to thirty (30) frames per second for most televisiontype video systems, the image appears to be jumping from frame image toframe image and smeared in the direction of motion as the eye smoothlytracts the average position of the moving image, but the image formed onthe retina is lagging, then leading the average position for half of theframe period each. With the ability to stagger the shutter timing suchthat each color plane captures and represents a different point in timeduring the frame, i.e. represents subframes or fields, the jutter willbe reduced as, on average, more of the reconstructed image energy willbe closer to the average position of the ideal smoothly moving image.The display means is similarly timed such that each color field isupdated with the same relative timing as the original electronicshutters. This aspect of the present invention, of displaced timing forthe color planes may be combined with the spatial displacement of thesample and reconstruction points, or it may be used in conventionalfully converged systems to equal advantage.

[0096] Note, that though the above examples used identical resolutioncamera sensor and projectors, such need not be the case and yet stillgain improved performance of the total system. Images captured directlyin a subpixel rendered format may be scaled up or down, to be shown oneither subpixelated or fully converged displays, and potentially retainthe performance benefit of the displaced image capture. For example,using the data set of FIG. 33B, the image may be processed, converted,and shown on a higher resolution conventional fully converged projectoror other display as shown in FIG. 33C. Note that the image quality ishigher than the image that would have been possible using the fullyconverged camera sensor arrangement of FIG. 31A.

[0097] An alternative multi-chip image sensor may have one of more ofthe sensors include a color filter array. One such example is shown inFIGS. 34A and 34B. FIG. 34A shows an arrangement of square sensors withred 3404 and green 3406 color filters affixed thereupon. FIG. 34Billustrates the lower resolution blue sensor plane. This blue sensor mayor may not have a blue filter depending upon on whether the image beamsplitter in the camera assembly was a dichroic filter. If a dichroicfilter that splits off the red and green colors from the blue is used,then the blue plane may not need an additional filter.

[0098] Other sensors with color filter arrays may be used to advantageto create subpixel rendered images that are directly displayed onsuitable subpixelated display means. For example, the conventional priorart Bayer pattern, and its improved variants, may be used with minimalprocessing. Said processing comprising the interpolation of surroundingred samples to fill in the missing red samples where the blue samplesinterrupt the red sample grid.

[0099] Scanners, devices that are used to convert still images, or moviefilm frames, to a digital or analog video format will also benefit fromthe teaching herein. Offset scanning, either mechanically orelectronically may provide a direct subpixel rendered image data set,similar to those described above, which may be used in like manner toimprove total system image quality.

[0100] Another embodiment would be to offset, electronically,physically, magnetically, and/or electrostatically the raster scan of amulti-tube video camera. Likewise, if the resulting direct subpixelrendered data set were delivered to a suitably matched display, such asa CRT or subpixelated flat panel display, the image quality would beincreased.

[0101] Conversely, color image printers, either photographic (filmprinter: CRT or laser scanning, spatial light modulator, etc.),xerographic (laser printer), or mechanical (ink jet, dye sublimation,dye transfer, etc.) may also benefit from the teaching herein, in whichsubpixel rendering of conventional high resolution image data sets ordirect printing of previously subpixel rendered image data sets is usedon a printer system with matching displaced color image planes.

[0102] One complete system that uses the teaching contained herein maycomprise original image capture using conventional color filmphotography and color film print presentation, with subpixel renderedfilm digitization, editing and manipulation, followed by subpixelrendered film printing. Such a system potentially would use modifiedequipment and processes presently used in film production, have the samesize image data files, etc., but due to the benefits of subpixelrendering techniques taught herein, exhibit significantly better imagequality in the final product. The process may have the additionalbenefit that the digitized image is in a subpixel rendered format thatmay be used in matching electronic cinema projectors with minimal or nofurther processing, again exhibiting improved image quality.

Additional Color Planes

[0103] Most conventional projector displays utilize three emittercolors, providing a color gamut that includes the inside of a trianglewhen charted on the 1931 CIE Color Chart, an example of which is shownin FIG. 24A. These colors are typically substantially red 2404, green2406, and blue 2402. The luminances of these color emitters aretypically unequal. For several reasons, some projectors displays areconstructed with a fourth color emitter. Prior art four color displaysusually use white as the fourth color. This is typically done toincrease the brightness of the display, as the colors are usuallycreated using dichroic filters. The white is created by removing a colorfilter; the light of the lamp which, being white 2408 already, isallowed to pass to the spatial light modulator unobstructed or modified.The four colors collectively are grouped into a pixel that may show anycolor within the triangle defined by the saturated colors, with theadded ability to show lower saturation colors at a higher brightness bythe addition of the appropriate amount of white.

[0104] For displays that are to be driven using subpixel rendering, thechoice of a non-filtered white color plane or field creates a seriousproblem. Subpixel rendering depends on the ability to shift the apparentcenter of luminance by varying the brightness of the subpixels. Thisworks best when each of the colors has the same perceptual brightness.Blue subpixels are perceived as substantially darker than the red andgreen, thus do not significantly contribute to the perception ofincreased resolution with subpixel rendering, leaving the task to thered and green subpixels. With the addition of an unfiltered white, thewhite color plane or field, being significantly brighter than both thered and green subpixels, the red and green lose much of theireffectiveness in subpixel rendering.

[0105] In an ideal display, the luminance of each of the subpixels wouldbe equal, such that for low saturation image rendering, each subpixelhas the same luminance weight. However, the human eye does not see eachwavelength of light as equally bright. The ends of the spectrum are seenas darker than the middle. That is to say that a given energy intensityof a green wavelength is perceived to be brighter than that same energyintensity of either red or blue. Further, due to the fact that the shortwavelength sensitive cones, the “S-cones”, those giving rise to thesensation of ‘blue’, do not feed the Human Vision System's luminancechannel, blue colors appear even darker.

[0106] In most prior art projector systems, the splitting of the whitespectrum is usually done so that the red 2404 and the blue 2402 colorpoints have the greatest color saturation as possible, while the green2406 point is formed from the middle of the spectrum, having both moreenergy and brightness than the red 2404 and blue 2402 combined.

[0107] One embodiment for a three color system shown in FIG. 24B entailsusing wider bands for red 2404 and blue 2402, pushing them up the charttowards the apex slightly to create new red 2404 b and blue 2402 b colorpoints, while the green 2406 b, being narrower, also is pushed towardthe apex. This increases the energy of the red 2404 b and blue 2402 b,while reducing the energy of the green 2406 b. The white point 2408remains in the same place. This remapping of the spectrum to the colortriangle improves the subpixel rendering performance, but shifts thecolor gamut. For many applications, this improvement may be quitesatisfactory and economical.

[0108] One embodiment that reduces the above problem adds a fourth colorthat substantially takes its energy from the shorter wavelength greenpart of the spectrum. In a system of dichroic beam splitters orregenerating color wheel assembly, this will reduce the energy beingused on the “green” color plane, splitting it between a yellowish green2506 and a cyan 2508 color as shown in FIG. 25. The total brightness andlight efficiency remains the same, but the red 2504, yellowish-green2506, and cyan 2508 beams have the substantially the same brightness. Afurther advantage is that the color gamut thus formed from the fourcolor system is wider than the prior art three color system. Yet afurther advantage of this invention is that the additional color beammay be independently modulated as a displaced subpixelated image, thusincreasing the image quality of the resulting subpixel rendered image,with three color planes with near equal perceived brightness.

[0109] With three planes of near equal perceived brightness, thearrangement of subpixelated color planes of FIG. 23 may be used to fullbenefit. FIG. 23 illustrates three images of the array of pixels shownin FIG. 8 overlaid with a shift of one third of a pixel each. A logicalpixel 128 is illustrated on the resulting image 126 in FIG. 23. The redpixel 130, green pixel 132, and “blue” (now possibly cyan) pixel 134overlap to form a smaller triangular area 136 that is at the center ofthe logical pixel. This overlap area is brightest, followed by the threeareas where there are only two pixels overlapping, while the areas withno overlap have the lowest brightness.

[0110] This process of increasing the number of color points anddisplaced color plane images can be performed again to yield a fivecolor system as shown in FIG. 26. Here, the red 2604 and blue 2602 maybe further pushed into their respective ‘corners’ by restricting theirbandpasses at the edges of the visible spectrum, increasing the colorgamut. The mid-spectrum is divided into three equally, perceptually,bright color points; greenish-yellow 2605, deep-green 2606, anddeep-cyan 2608. This, along with the red 2604, gives four planes ofeffective subpixel rendered image. For good measure, the blue plane maybe made coincident, fully converged, with the red to add to itsbrightness, giving a magenta color plane. These four colors may be usedwith arrangement of pixels of FIG. 30 to advantage.

[0111] In yet another embodiment, there is a possibility for integratinga “front-to-back” system (i.e. from image capture and/or generation toimage render) using five colors. Each of the colors is subpixelrendered, from the camera to the projector. The color points are chosencarefully to both cover a wide gamut and be approximately the sameluminance. Each color comes from narrow spectral band defined bydichroic filter-beam splitters. When the projector recombines the light,save for random loss, all of the light from the lamp is used to recreatethe same white light.

[0112] Several color arrangements are possible. For example, here aretwo that use the colors R=red; Y=yellow; C=cyan; G=green and B=blue—ineither a diamond or square matrix layout: C Y C Y RYRY G R G CGCG Y C YC RYRY R G R CGCG

[0113] Of course, other matrices are possible—with other colors alsoselected. It should also be possible to use the blue plane at a lowerresolution.

[0114] As well as separating the sample points of each color in space,by subpixel rendering, the color plane samples are displaced in time aswell. Not only will this reduce temporal aliasing of moving objects, butit will significantly reduce jutter. The four longer wavelength colorsare shuttered on a rotating basis, 90 degrees from the preceding andfollowing color plane. That means there is also a color shuttered at 180degrees from each color. The blue plane may be shuttered at any pointsince it will not greatly add to brightness. But if one of the othercolors is the dimmest, the blue may be shuttered with it to keep itstransition roughly the same amplitude as the others to eliminateflicker. With four major colors to work with, the addressability isincreased by a factor of four and the MTF is doubled in each axis.

[0115] This process of breaking up the spectrum and increasing thenumber of subpixel rendering planes may be performed up to any arbitrarynumber, N.

Flicker Reduction in Field Sequential Color Systems

[0116] The perception of flicker in Field Sequential Color (FSC) systemsis primarily caused by the unequal luminances of the color componentsthat are time sequentially flashed onto the screen or to the viewer'seyes. The largest luminance difference in prior art three color systemsis between the green color and the blue color, the blue color havingcomparatively little or no perceived luminance. Prior art methods ofreducing the perception of flicker have included increasing the temporalfrequency at which the three or more colors fields are presented.However, for some spatial light modulators, this is impractical eitherdue to the bandwidth limits being less than that required to transferthe image of each field or to the time required for the spatial lightmodulator to present a high contrast image of the field (e.g. LiquidCrystal response time) being too long for the desired field rate.

[0117] A novel method of reducing the perception of flicker comprisesthe reduction of the total time that the dark, low luminance, color,such as blue, is presented to the viewer. Another novel method is toincrease only the dark, low luminance, color frequency. Additionally,the two methods listed above may be combined to advantage.

[0118] For direct view applications, Light Emitting Diodes (LEDs) may beused as the illuminants. In this case, the practice is to use very briefflashes of monochromatic light for each color field. Thus, the set-uptime for the spatial light modulator is often the limiting factor forthe field and frame rates. As described above one method to reduceflicker perception is to increase the blue flash rate. In this case,instead of the prior art order of color flashes, which is typicallysomething like: . . . red, green, blue, red, green, blue, red, green,blue . . . , the following order of color flashes may be substituted: .. . red, blue, green, blue, red, blue, green, blue . . . , etc. Notethis will slow the frame rate if the field rate is kept constant. Thiswill however, increase the frequency of the blue flashes, countered bythe higher luminance flashes, namely red and green in the above example,reducing the perception of flicker. If the time for setting up the bluefield image on the spatial light modulator may be reduced by a suitablemethod, the time between the red or green fields and the blue fieldflash may be reduced to maintain the same frame rate as the prior artfield order. In each of the above, the total illumination intensity ofeach color component, averaged over the frame, is adjusted to maintainthe desired white point; Specifically, the intensity of the doubled blueflashes may be reduced in half, or one may be one fourth (¼) and theother flash may be three fourths (¾) of the single flash intensity.

[0119] For projectors that use color filter wheels, the color wheel maybe modified to provide the same or similar novel arrangement of colorflashes as above. In FIG. 37, a prior art color wheel arrangement 3700is illustrated. In this color wheel 3700 there are three color filterregions blue 3702, red 3704, and green 3706. The color wheel spins atthe same rate as the frame rate of the display system, illuminating thespatial light modulator: . . . red, green, blue, red, green, blue, red,green, blue . . . , etc. FIGS. 38A, 38B, 38C, and 38D illustrate novelcolor wheels, with various combinations of reduced low luminance colorcomponent (e.g. blue) time or doubled low luminance color componentfrequency, or combinations of the two.

[0120]FIG. 38A illustrates a novel color filter wheel 3800 that reducesthe size of the low luminance color (e.g. blue) filter region 3802.Reducing the time that the blue illumination is the only light beingviewed reduces the strength of the Fourier signal energy from theluminance variation. Reduced Fourier signal energy reduces thevisibility of the perceived flicker.

[0121]FIG. 38D illustrates a novel color filter wheel 3830 that has fourcolor regions, two of which are low luminance (e.g. blue) color 3832,while the two are higher luminance colors. These may be red 3834 andgreen 3836. Thus, this may provide the following color field sequence: .. . red, blue, green, blue, red, blue, green, blue . . . , etc. Notethis will slow the frame rate if the field rate is kept constant. Thiswill however, increase the frequency of the blue flashes, countered bythe higher luminance flashes, namely red and green in the above example,reducing the perception of flicker.

[0122] If the time for setting up the blue field image on the spatiallight modulator may be reduced by a suitable method, the field time maybe reduced to maintain the same frame rate as the prior art field order.FIGS. 38B and 38C illustrate examples where both the blue time period isreduced and the frequency increased. The color filter wheel 3810 of FIG.38B has the property that the combined angular area and/or angulardistance of the two blue regions 3812 is the same of that of either ofthe other two colors, red 3814 or green 3816. This gives the advantagethat the illumination balance is identical to the prior art color filterwheel 3700 of FIG. 37. FIG. 38C illustrates a color filter wheel 3820that has both doubled and reduced angular area and/or angular distanceblue filter regions 3822. This doubles the blue dark frequency andreduces the total time at that lower luminance, reducing the perceptionof flicker.

[0123]FIG. 39A illustrates a novel color filter wheel 3900 that places avery low luminance and low radiance (e.g. black) filter region 3912opposite the low luminance color (e.g. blue) filter region 3902. Theopposition of black and blue doubles the temporal frequency of lowluminance, reducing the perception of flicker. FIG. 39B illustrates thesame color filter wheel 3900 with the addition of two additional verylow luminance color (e.g. black) filter regions 3912 b and 3912 b thatbreak up the red filter region 3904 and green filter region 3906 of FIG.39A into two red filter regions 3904 b and 3904 b and two green filterregions 3906 b and 3906 b. The spatial light modulator may remaindisplaying the same red or green color field information during theblack time intervals created by the superimposed black filter region3912 b or 3912 b. The presence of the two additional black filterregions 3912 b and 3912 b further increases the temporal frequency ofthe low luminance signal, reducing the perception of flicker.

[0124]FIG. 40 illustrates a novel color filter wheel 4000 of fourcolors. The fourth color may be comprised of high transmissive, andtherefore, high luminance (e.g. white or clear) regions 4008. Theseclear regions 4008 may be placed in opposition, such that their higherluminance temporal frequency is doubled, reducing perception of flicker.The low luminance color (e.g. blue) regions 4002 may be placed inopposition, such that their lower luminance temporal frequency isdoubled, reducing the perception of flicker. Further, the high luminanceand low luminance regions may be placed next to each other such that oneleads or follows the other. This juxtaposition creates higher temporalfrequency Fourier signal components than if they were not so juxtaposed,reducing the perception of flicker.

[0125] In addition to using the timing of Light Emitting Diodes and thetransmission sequence of color filter wheels, other color timing methodsmay be similarly modified. For example, the use of Liquid Crystal basedPI cell color modulators, colored fluorescent backlights, orelectrically controlled, color selecting, holograms may be modified suchthat the timing follows the above examples.

Bandwidth Reduction

[0126] Bandwidth reduction, to allow faster transfer of data to thespatial light modulator, or to allow greater image compression fortransmission or storage, may be facilitated by another embodiment. Thisbandwidth reduction may enable the reduced time to form the image on thespatial light modulator, which in turn may enable reduced time and/ordivided low luminance color field display as disclosed above. Thisbandwidth reduction may be implemented with spatio-temporally displacedfiltering and reconstruction to maintain addressability and ModulationTransfer Function, maintaining image quality.

[0127]FIGS. 41, 42A, 42B, 42C, and 42D illustrate a data set that isspatio-temporally displaced filtered and reconstructed. FIG. 41illustrates the original data set 4100. It may also represent a matchingprior art spatial light modulator 4100 which is to be used toreconstruct the spatio-temporally displaced filtered data set. ExaminingFIG. 42A, data points 4205 are grouped together into larger data points4215, applying a suitable filter to the original data points 4205,perhaps a simple box filter. This creates a lower resolution image dataset, with less data points, thus reducing the bandwidth required totransmit the image. Turning to FIG. 42B, again, data points 4205 aregrouped together into larger data points 4225. Note that these largerdata points 4225 comprise a different grouping of original data points4205, than does the first larger data points 4215. The groupings 4215and 4225 are displaced diagonally by one half. This is functionallysimilar to the displaced filtered and reconstructed image of FIG. 20.When these two data sets are sequentially displayed, one after another,each time that color field is displayed, the temporal integration of thehuman eye composites the two lower resolution images as a higherresolution image, in a manner very similar to that described above forimages that are simultaneously presented. Examining FIGS. 42C and 42D,note that each groups original data points 4205 into larger data points4235 and 4245 respectively. Again, note that the larger groupings aredisplaced from one another, and from both of the previously discussedgroups 4215 and 4225. When all four are presented sequentially, eachtime for that color field, the temporal integration of the human eyecomposites the four lower resolution images as a higher resolutionimage, in a manner very similar to that described above for images thatsimultaneously presented. This is functionally similar to the displacedfiltered and reconstructed image of FIG. 30.

[0128] While the above example used square grid data samples, boxfilters, of two by two original data points 4205 going to each outputdata resample 4215, 4225, 4235, and 4245, it will be appreciated thatother combinations of input samples (e.g. 3×3, 4×5, etc), filters (e.g.tent, Gaussian, Difference-Of-Gaussians, etc), and output resample grid(e.g. FIGS. 6, 7, and 8, etc.) will also function in a similar manner.All such variations are contemplated.+

[0129] While the invention has been described with reference toexemplary implementations and embodiments, it will be understood thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings without departing from the essential scopethereof. Therefore, it is intended that the invention not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this invention, but that the invention will include allembodiments falling within the scope of the appended claims.

What is claimed is:
 1. An image display system comprising: an outputunit; and means for displaying a plurality of color frames on the outputunit, wherein each color frame is subpixelated and displayed over time,one of the color planes is a color plane of a low luminance color, andthe low luminance color plane is displayed with greater frequency overtime than other displayed color frames.
 2. The image display system ofclaim 1, wherein the means for displaying further comprises: a set ofmonochromatic light emitting diodes for a direct view output unit. 3.The image display system of claim 1, wherein the means for displayingfurther comprises: a set of color filters placed upon a color wheel suchthat the regions of low luminance color filter upon said color wheel isgreater in number than the other color filters.
 4. The image displaysystem of claim 1, wherein the low luminance color plane issubstantially blue and the blue color plane is displayed twice as oftenas other color planes.
 5. The image display system of claim 4, whereinthe blue color plane is displayed with approximately half of theintensity of the other color planes.
 6. The image display system ofclaim 4, wherein the blue color plane is displayed at a first intensityat a first time and the blue color plane is displayed at a secondintensity at a second time.
 7. An image display system comprising: anoutput unit; a means for displaying each of a plurality of color frames,each color frame is subpixelated and displayed over time, one of thecolor planes is a color plane of a low luminance color, and the lowluminance color plane is displayed for a time period less than otherdisplayed color frames.
 8. The image display system of claim 7, whereinthe means for displaying each of a plurality of color frames furthercomprises: a set of color filters placed upon a color wheel such that atotal angular distance of a low luminance color filter upon the colorwheel is smaller in length than the other color filters on the colorwheel.
 9. The image display system of claim 8, wherein the low luminancecolor filter is divided into separate angular regions upon the colorwheel.
 10. The image display system of claim 4, further comprising: atleast one high luminance color filter placed upon said color wheel suchthat the at least one high luminance color filter is placed oppositesaid low luminance color filter upon the color wheel.
 11. The imagedisplay system of claim 10, wherein the at least one high luminancecolor filters one of a group comprising either white or clear filter.12. A color wheel for a display system comprising: a set of colorfilters including at least one low luminance color filter such that atotal angular distance of the low luminance color filter is smaller inlength than the other color filters.
 13. The color wheel of claim 12,wherein the low luminance color filter is divided into separate angularregions.
 14. The color wheel of claim 12, wherein the set of colorfilter includes at least one high luminance color filter such that theat least one high luminance color filter is placed opposite the lowluminance color filter upon the color wheel.
 15. The color wheel ofclaim 14, wherein the at least one high luminance color filter is one ofa group comprising either white or clear color filter.